# man > ss(8)

[_SS_(8)](https://www.chedong.com/phpMan.php/man/SS/8/markdown)                                  System Manager's Manual                                 [_SS_(8)](https://www.chedong.com/phpMan.php/man/SS/8/markdown)

## NAME
       ss - another utility to investigate sockets

## SYNOPSIS
       **ss **[_options_] _[_ _FILTER_ _]_

## DESCRIPTION
       **ss  **is  used to dump socket statistics. It allows showing information similar to _netstat_.  It
       can display more TCP and state information than other tools.


## OPTIONS
       When no option is used ss displays a list of open non-listening sockets  (e.g.  TCP/UNIX/UDP)
       that have established connection.

### -h, --help
              Show summary of options.

### -V, --version
              Output version information.

### -H, --no-header
              Suppress header line.

### -O, --oneline
              Print each socket's data on a single line.

### -n, --numeric
              Do  not  try  to resolve service names. Show exact bandwidth values, instead of human-
              readable.

### -r, --resolve
              Try to resolve numeric address/ports.

### -a, --all
              Display both listening and non-listening (for TCP this means established  connections)
              sockets.

### -l, --listening
              Display only listening sockets (these are omitted by default).

### -o, --options
              Show timer information. For TCP protocol, the output format is:

              timer:(<timer_name>,<expire_time>,<retrans>)

              **<timer_name>**
                     the name of the timer, there are five kind of timer names:

                     **on  **: means one of these timers: TCP retrans timer, TCP early retrans timer and
                     tail loss probe timer

                     **keepalive**: tcp keep alive timer

                     **timewait**: timewait stage timer

                     **persist**: zero window probe timer

                     **unknown**: none of the above timers

              **<expire_time>**
                     how long time the timer will expire

              **<retrans>**
                     how many times the retransmission occurred

### -e, --extended
              Show detailed socket information. The output format is:

              uid:<uid_number> ino:<inode_number> sk:<cookie>

              **<uid_number>**
                     the user id the socket belongs to

              **<inode_number>**
                     the socket's inode number in VFS

              **<cookie>**
                     an uuid of the socket

### -m, --memory
              Show socket memory usage. The output format is:

              skmem:(r<rmem_alloc>,rb<rcv_buf>,t<wmem_alloc>,tb<snd_buf>,
                            f<fwd_alloc>,w<wmem_queued>,o<opt_mem>,
                            bl<back_log>,d<sock_drop>)

              **<rmem_alloc>**
                     the memory allocated for receiving packet

              **<rcv_buf>**
                     the total memory can be allocated for receiving packet

              **<wmem_alloc>**
                     the memory used for sending packet (which has been sent to layer 3)

              **<snd_buf>**
                     the total memory can be allocated for sending packet

              **<fwd_alloc>**
                     the memory allocated by the socket as cache, but not used for receiving/sending
                     packet yet. If need memory to send/receive packet, the  memory  in  this  cache
                     will be used before allocate additional memory.

              **<wmem_queued>**
                     The memory allocated for sending packet (which has not been sent to layer 3)

              **<opt_mem>**
                     The memory used for storing socket option, e.g., the key for TCP MD5 signature

              **<back_log>**
                     The  memory used for the sk backlog queue. On a process context, if the process
                     is receiving packet, and a new packet is received, it will be put into  the  sk
                     backlog queue, so it can be received by the process immediately

              **<sock_drop>**
                     the number of packets dropped before they are de-multiplexed into the socket

### -p, --processes
              Show process using socket.

### -T, --threads
              Show thread using socket. Implies -p.  **-p**.

### -i, --info
              Show internal TCP information. Below fields may appear:

              **ts     **show string "ts" if the timestamp option is set

              **sack   **show string "sack" if the sack option is set

              **ecn    **show string "ecn" if the explicit congestion notification option is set

              **ecnseen**
                     show string "ecnseen" if the saw ecn flag is found in received packets

              **fastopen**
                     show string "fastopen" if the fastopen option is set

              **cong_alg**
                     the congestion algorithm name, the default congestion algorithm is "cubic"

              **wscale:<snd_wscale>:<rcv_wscale>**
                     if  window scale option is used, this field shows the send scale factor and re‐
                     ceive scale factor

              **rto:<icsk_rto>**
                     tcp re-transmission timeout value, the unit is millisecond

              **backoff:<icsk_backoff>**
                     used for exponential backoff re-transmission, the actual re-transmission  time‐
                     out value is icsk_rto << icsk_backoff

              **rtt:<rtt>/<rttvar>**
                     rtt  is the average round trip time, rttvar is the mean deviation of rtt, their
                     units are millisecond

              **ato:<ato>**
                     ack timeout, unit is millisecond, used for delay ack mode

              **mss:<mss>**
                     max segment size

              **cwnd:<cwnd>**
                     congestion window size

              **pmtu:<pmtu>**
                     path MTU value

              **ssthresh:<ssthresh>**
                     tcp congestion window slow start threshold

              **bytes_acked:<bytes_acked>**
                     bytes acked

              **bytes_received:<bytes_received>**
                     bytes received

              **segs_out:<segs_out>**
                     segments sent out

              **segs_in:<segs_in>**
                     segments received

              **send <send_bps>bps**
                     egress bps

              **lastsnd:<lastsnd>**
                     how long time since the last packet sent, the unit is millisecond

              **lastrcv:<lastrcv>**
                     how long time since the last packet received, the unit is millisecond

              **lastack:<lastack>**
                     how long time since the last ack received, the unit is millisecond

              **pacing_rate <pacing_rate>bps/<max_pacing_rate>bps**
                     the pacing rate and max pacing rate

              **rcv_space:<rcv_space>**
                     a helper variable for TCP internal auto tuning socket receive buffer

              **tcp-ulp-mptcp flags:[MmBbJjecv] token:<rem_token(rem_id)/loc_token(loc_id)> seq:<sn>**
              **sfseq:<ssn> ssnoff:<off> maplen:<maplen>**
                     MPTCP subflow information

       **--tos  **Show ToS and priority information. Below fields may appear:

              **tos    **IPv4 Type-of-Service byte

              **tclass **IPv6 Traffic Class byte

              **class_id**
                     Class id set by net_cls cgroup. If class is zero this  shows  priority  set  by
                     SO_PRIORITY.

### --cgroup
              Show cgroup information. Below fields may appear:

              **cgroup **Cgroup v2 pathname. This pathname is relative to the mount point of the hierar‐
                     chy.

### --tipcinfo
              Show internal tipc socket information.

              **-K, --kill**
                     Attempts  to forcibly close sockets. This option displays sockets that are suc‐
                     cessfully closed and silently skips sockets that the kernel  does  not  support
                     closing. It supports IPv4 and IPv6 sockets only.

              **-s, --summary**
                     Print  summary  statistics.  This  option does not parse socket lists obtaining
                     summary from various sources. It is useful when amount of sockets  is  so  huge
                     that parsing /proc/net/tcp is painful.

              **-E, --events**
                     Continually display sockets as they are destroyed

              **-Z, --context**
                     As  the  **-p **option but also shows process security context. If the **-T **option is
                     used, also shows thread security context.

                     For [**netlink**(7)](https://www.chedong.com/phpMan.php/man/netlink/7/markdown) sockets the initiating process context is displayed as follows:

                            1.  If valid pid show the process context.

                            2.  If destination is kernel (pid = 0) show kernel initial context.

                            3.  If a unique identifier has been allocated by the kernel  or  netlink
                                user,  show  context  as "unavailable". This will generally indicate
                                that a process has more than one netlink socket active.

              **-z, --contexts**
                     As the **-Z **option but also shows the socket context. The socket context is taken
                     from the associated inode and is not the actual socket context held by the ker‐
                     nel. Sockets are typically labeled with the context of  the  creating  process,
                     however the context shown will reflect any policy role, type and/or range tran‐
                     sition rules applied, and is therefore a useful reference.

              **-N NSNAME, --net=NSNAME**
                     Switch to the specified network namespace name.

              **-b, --bpf**
                     Show  socket  classic BPF filters (only administrators are allowed to get these
                     information).

              **-4, --ipv4**
                     Display only IP version 4 sockets (alias for -f inet).

              **-6, --ipv6**
                     Display only IP version 6 sockets (alias for -f inet6).

              **-0, --packet**
                     Display PACKET sockets (alias for -f link).

              **-t, --tcp**
                     Display TCP sockets.

              **-u, --udp**
                     Display UDP sockets.

              **-d, --dccp**
                     Display DCCP sockets.

              **-w, --raw**
                     Display RAW sockets.

              **-x, --unix**
                     Display Unix domain sockets (alias for -f unix).

              **-S, --sctp**
                     Display SCTP sockets.

              **--tipc **Display tipc sockets (alias for -f tipc).

              **--vsock**
                     Display vsock sockets (alias for -f vsock).

              **--xdp  **Display XDP sockets (alias for -f xdp).

              **-M, --mptcp**
                     Display MPTCP sockets.

              **--inet-sockopt**
                     Display inet socket options.

              **-f FAMILY, --family=FAMILY**
                     Display sockets of type FAMILY.  Currently  the  following  families  are  sup‐
                     ported: unix, inet, inet6, link, netlink, vsock, tipc, xdp.

              **-A QUERY, --query=QUERY, --socket=QUERY**
                     List  of  socket tables to dump, separated by commas. The following identifiers
                     are understood: all, inet, tcp, udp, raw, unix,  packet,  netlink,  unix_dgram,
                     unix_stream,   unix_seqpacket,  packet_raw,  packet_dgram,  dccp,  sctp,  tipc,
                     vsock_stream, vsock_dgram, xdp, mptcp. Any item in the list may  optionally  be
                     prefixed  by  an  exclamation mark (**!**)  to exclude that socket table from being
                     dumped.

              **-D FILE, --diag=FILE**
                     Do not display anything, just dump raw information about TCP  sockets  to  FILE
                     after applying filters. If FILE is - stdout is used.

              **-F FILE, --filter=FILE**
                     Read  filter information from FILE.  Each line of FILE is interpreted like sin‐
                     gle command line option. If FILE is - stdin is used.

              **FILTER := [ state STATE-FILTER ] [ EXPRESSION ]**
                     Please take a look at the official documentation for details regarding filters.


## STATE-FILTER
       **STATE-FILTER **allows one to construct arbitrary set of states to match. Its syntax is sequence
       of keywords state and exclude followed by identifier of state.

       Available identifiers are:

              All standard TCP states:  **established**,  **syn-sent**,  **syn-recv**,  **fin-wait-1**,  **fin-wait-2**,
              **time-wait**, **closed**, **close-wait**, **last-ack**, **listening **and **closing.**

              **all **- for all the states

              **connected **- all the states except for **listening **and **closed**

              **synchronized **- all the **connected **states except for **syn-sent**

              **bucket **- states, which are maintained as minisockets, i.e.  **time-wait **and **syn-recv**

              **big **- opposite to **bucket**


## EXPRESSION
       **EXPRESSION  **allows  filtering based on specific criteria.  **EXPRESSION **consists of a series of
       predicates combined by boolean operators. The  possible  operators  in  increasing  order  of
       precedence  are  **or **(or | or ||), **and **(or & or &&), and **not **(or !). If no operator is between
       consecutive predicates, an implicit **and **operator is assumed. Subexpressions  can  be  grouped
       with "(" and ")".

       The following predicates are supported:


### {dst|src} [=] HOST
              Test if the destination or source matches HOST. See HOST SYNTAX for details.

### {dport|sport} [OP] [FAMILY:]:PORT
              Compare the destination or source port to PORT. OP can be any of "<", "<=", "=", "!=",
              ">="  and  ">". Following normal arithmetic rules. FAMILY and PORT are as described in
              HOST SYNTAX below.

### dev [=|!=] DEVICE
              Match based on the device the connection uses. DEVICE can either be a device  name  or
              the index of the interface.

### fwmark [=|!=] MASK
              Matches  based  on  the fwmark value for the connection. This can either be a specific
              mark value or a mark value followed by a "/" and a bitmask of which bits to use in the
              comparison. For example "fwmark = 0x01/0x03" would match if the two least  significant
              bits of the fwmark were 0x01.

### cgroup [=|!=] PATH
              Match if the connection is part of a cgroup at the given path.

### autobound
              Match  if  the  port or path of the source address was automatically allocated (rather
              than explicitly specified).

       Most operators have aliases. If no operator is supplied "=" is assumed.  Each of the  follow‐
       ing groups of operators are all equivalent:

              • = == eq

              • != ne neq

              • > gt

              • < lt

              • >= ge geq

              • <= le leq

              • ! not

              • | || or

              • & && and

## HOST SYNTAX
       The general host syntax is [FAMILY:]ADDRESS[:PORT].

       FAMILY  must  be  one of the families supported by the -f option. If not given it defaults to
       the family given with the -f option, and if that is also missing, will assume either inet  or
       inet6.  Note  that all host conditions in the expression should either all be the same family
       or be only inet and inet6. If there is some other mixture of families, the results will prob‐
       ably be unexpected.

       The form of ADDRESS and PORT depends on the family used. "*" can be used as  a  wildcard  for
       either the address or port. The details for each family are as follows:

       **unix   **ADDRESS  is  a  glob  pattern (see [**fnmatch**(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown)) that will be matched case-insensitively
              against the unix socket's address. Both path and abstract names  are  supported.  Unix
              addresses do not support a port, and "*" cannot be used as a wildcard.

       **link   **ADDRESS  is the case-insensitive name of an Ethernet protocol to match. PORT is either
              a device name or a device index for the desired link device, as seen in the output  of
              ip link.

### netlink
              ADDRESS   is   a   descriptor  of  the  netlink  family.  Possible  values  come  from
              /etc/iproute2/nl_protos. PORT is the port id of the socket, which is usually the  same
              as the owning process id. The value "kernel" can be used to represent the kernel (port
              id of 0).

       **vsock  **ADDRESS is an integer representing the CID address, and PORT is the port.

       **inet **and **inet6**
              ADDRESS  is  an ip address (either v4 or v6 depending on the family) or a DNS hostname
              that resolves to an ip address of the required version. An ipv6 address  must  be  en‐
              closed in "[" and "]" to disambiguate the port separator. The address may additionally
              have  a prefix length given in CIDR notation (a slash followed by the prefix length in
              bits). PORT is either the numerical socket port, or the service name for the  port  to
              match.


## USAGE EXAMPLES
### ss -t -a
              Display all TCP sockets.

### ss -t -a -Z
              Display all TCP sockets with process SELinux security contexts.

### ss -u -a
              Display all UDP sockets.

### ss -o state established '( dport = :ssh or sport = :ssh )'
              Display all established ssh connections.

       **ss -x src /tmp/.X11-unix/***
              Find all local processes connected to X server.

### ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 193.233.7/24
              List  all  the  tcp sockets in state FIN-WAIT-1 for our apache to network 193.233.7/24
              and look at their timers.

### ss -a -A 'all,!tcp'
              List sockets in all states from all socket tables but TCP.

## SEE ALSO
       [**ip**(8)](https://www.chedong.com/phpMan.php/man/ip/8/markdown),
       **RFC **793 - <https://tools.ietf.org/rfc/rfc793.txt> (TCP states)


## AUTHOR
       _ss_ was written by Alexey Kuznetsov, <<kuznet@ms2.inr.ac.ru>>.

       This manual page was written by Michael Prokop <<mika@grml.org>> for the  Debian  project  (but
       may be used by others).

                                                                                               [_SS_(8)](https://www.chedong.com/phpMan.php/man/SS/8/markdown)